1. Field of the Invention
The present invention relates generally to the shaker tables to which manufactured devices are mounted for vibrational testing. More particularly, the present invention relates to a specific mounting table and to the exciters or vibrators mounted thereto.
2. Description of the Prior Art
Shaker tables for testing the reliability of manufactured devices are well known. Such shaker tables are used either under laboratory conditions or in conjunction with an assembly line. Often, shaker tables are mounted within thermal chambers, which gives the added flexibility of testing for defects in the manufactured product which may be exposed by elevated temperature or temperature cycling.
The shaker tables typically include a platform or mounting table upon which a device to be tested is mounted. Exciters or vibrators are attached to the mounting table to vibrate the device. It is necessary to provide an even distribution of the vibration amplitude, magnitude, direction and frequency in a range. Typical of such arrangements is U.S. Pat. No. 4,735,089 issued to Richard L. Baker, et al. That patent and others attempt to establish a uniform amplitude to the mounting table from the exciters over the range of frequencies generated.
The Baker patent identifies a problem with rigid shaker tables in achieving the objective of creating random vibration of substantially equal amplitude over the range of frequencies in a multi-axial direction. Baker does so by use of a flexible shaker table that is said to resolve potential resonance problems normally inherent in rigid mounting tables. The end result of this multi-axial excitation is a relatively complex mounting table or platform, having multiple layers, multiple connectors and multiple potential wear points.
My co-pending application discloses and claims a honeycomb table structure which achieves random vibration in multi-axial directions in a relatively rigid table. The present invention is a improvement of the table disclosed in my pending application.
It is also inherent in the manufacture and use of shaker tables that energy, in the form of compressed air to operate the exciters, will be required. Heretofore, the exciters that have incorporated resilient polymeric materials in the piston portion of the cylinder piston combination of the exciter, have been unable to cycle at higher rates for a given air pressure. None of these pistons have been cooled by the operating air pressure. The rapid movements of the piston in the cylinder have generated heat that melted the materials.
A prior art vibrator is shown in U.S. Pat. No. 3,376,790. There has never been a pneumatic exciter specifically made for the requirements of shaker tables. Specifically, exciters which individually vary the impact cycle rate between the piston and cylinder of the exciter have not been known.